7mge BHG

[.TheJones-]

First let me apologize for re-posting. I attempted to read other threads on this issue but I am just not understanding. (Yay he can search now) I had a JDM swap 7mge. HG blew after 800 miles. The guy followed all data instead on listening to what i said about the forums of over-torquing them.

What I got from the forums;

- only use a MHG if I can have the heads and block machined.
-MHG may be overkill if I don't plan on putting any turbo
-I am wasting my money by doing all this because my car is not raced


-if I use an OEM or Cometic(not sure what that is) HG I just need to have it torqued way past specs?

-using the cheaper HG's will allow for imperfections in the head and block that the MHG would not allow.

-using the these OEM or Cometic gaskets sounds like my best bet since a "stock" 7mge that runs properly is all I really want. I say "stock" because I put a headers back exhaust and am currently looking for an intake.

So did I understand what I read properly? Please use idiot terms with me. I am completely clueless, I was a GM 4x4 nut before this. And thanks again for tolerating a re-post!

 

[bioskyline]

if its staying mostly stock id go for a new OEM style HG, casue yeah a mhg would be overkill. a stock one torqued properly will probably outlast the car/motor till it needs a full rebuild.

you will still probably need to get the head machined, as it more than likely has damage from the gasket failing. check the block over with a straigt/flat edge at the point of failure.

BUT one thing that does happen when a hg fails is the bottom end bearings fail not long after, due to antifrezze contamination in the oil. so dont be surprisezed if later down the road you end up with rod knock.

 

[CRE]

Cometic is a brand of MLS HG. It does require the same prep as any other MHG; It's just more forgiving if there's texture from the machining than some other types.

 

[suprarx7nut]

Use an oem gasket from Toyota. Torque to ~ 72 ft-lbs. Get the head machines flat and clean the block with gasket remover and a scraper.

Should be just fine for a daily.

Sent from my ADR6400L using Tapatalk

 

[hvyman]

72-75 on a stock style hg. Use arp spec that they come with.

For a 7mge id just get a felpro or oem head gasket and use arp bolts. Or spend 20 more and get studs. OR find some used ones.

And its not really way over spec. Its what the spec should be. 58ft lbs was never enough torque for the 7m and gasket design. Same thing happened to the 4 runners but they got a recall.

 

[metaphysico]

Also a commonly overlooked thing is when you are torquing the bolts down you cant just put them in dry, if the guy did this then it was way under spec. I dont remember the specs but all in all a dry bolt loses torque by trying to overcome friction between the threads, if you use oil you have less friction and more direct torque, if you use moly lube (it comes with arps) there is even less friction. I am wanting to say that a dry bolt loses something like 60% of its torque due to friction, a bolt with oil on it loses 30% or so, and with moly lube you loose 10% due to friction. What happens a lot of times when people have blow head gaskets in quick time from when it was done they dont lube the bolts, then they go with arps thinking that will solve the problem and they come with lube so they put the lube on them and they hold, so the person thinks it was all the arps that fixed it but in reality some times its just the lube being put on it.

 

[Nick M]

Stock headbolts are as good as the ARP bolts. The composite gasket is used because iron and aluminum are dissimilar metals. So is a circuit breaker. So guess what happens when you get it hot. The composite gasket has give to keep its seal. A MHG is done and tightened to stop the natural warpage that occurs with the dissimilar metals. They hold with more force than the block and head will try to expand.

The good thing with Fel-Pro is you don't have to buy the whole head kit like you do with Toyota. With any headgasket, metal or not, the head and block must be flat within specs. Smoothness isn't the concern, but it still has to be flat, or you will be doing it again.

 

[suprarx7nut]

Stock headbolts are as good as the ARP bolts. The composite gasket is used because iron and aluminum are dissimilar metals. So is a circuit breaker. So guess what happens when you get it hot. The composite gasket has give to keep its seal. A MHG is done and tightened to stop the natural warpage that occurs with the dissimilar metals. They hold with more force than the block and head will try to expand.

The good thing with Fel-Pro is you don't have to buy the whole head kit like you do with Toyota. With any headgasket, metal or not, the head and block must be flat within specs. Smoothness isn't the concern, but it still has to be flat, or you will be doing it again.

Huh? You can get the Toyota HG by itself. It's around $80 typically.

 

[Turbo Habanero]

Just go OEM Gasket (one with copper inserts) Arp headstuds (make sure to lube them up) Torque down to 90ft lbs drive for 500-800mi crack the bolts one by one re-torque down to 90.

And always get the Head re-surfaced.